Normally, enough moisture is present in ambient air entrained
into a venturi barrel to provide sufficient humidification.
Patients however, with thick mucous secretions in the airway,
undergoing controlled oxygen therapy may require additional
To provide this a humidity adaptor has to be attached to the
venturi barrel, with the open end away from the mask and connected
to either a large volume nebuliser or humidifier. When oxygen is
delivered at a flow rate of 1-4 l/min by mask, nasal cannula or
nasal catheters, the oropharynx or nasopharynx provide adequate
humidification. At a higher flow rate or when oxygen is delivered
directly to the trachea, humidification is necessary.
Ultimately it might be necessary to increase the moisture
content of the inspired gases in order to prevent the possible
detrimental effect of dry gases on the airway structure. The
humidity adaptor fixes over a venturi barrel as normal.
The adaptor has a 22mm arm which is connected to a humidifier
via 22mm corrugated (elephant) tubing. Humidified air is
transported from the bubble humidifier or heated humidifier to the
humidity adaptor, then it is mixed with fixed concentration oxygen.
This is the most accurate method of giving Fixed Concentration
Humidified Oxygen to the patient.